Currently, mobile communication technologies are evolving towards higher frequency, larger carrier bandwidth, higher data rate and more heterogeneous layers. Future mobile networks, e.g., the 5th Generation (5G) mobile networks, are likely to be a combination of the 3rd Generation (3G) technologies, the 4th Generation (4G) technologies and new features such as Ultra-Density Network (UDN) or millimeter Wave Radio Access Technology (mmW-RAT).
FIG. 1 shows an exemplary structure of an mmW-RAT network. As shown in FIG. 1, a cluster of Access Nodes (ANs) 104, 106 and 108 are connected to and controlled by a Central Control Unit (CCU) 102. A User Equipment (UE) 110 is served by the ANs 104 and 106 via radio links, Link #1 and Link #2, respectively. The CCU 102 coordinates resource allocations in the cluster of ANs.
One mmW-RAT carrier may consist of a number of sub-carriers. Each sub-carrier can have a certain bandwidth, e.g. 100 MHz, and the total carrier bandwidth can be up to 1 GHz or 2 GHz. FIG. 2 illustrates an exemplary template frame containing 4 sub-carriers. In FIG. 2, the smallest resource grid in time and frequency is referred to as a resource element (RE) or an Atomic Scheduling Unit (ASU). As an example, the hatched REs in FIG. 2 can be allocated to Link #1. Among the hatched REs, those labeled as “D” are dedicated resources and those labeled as “S” are shared resources. Link #1 has the highest priority to access the dedicated resources and any neighboring link (e.g., Link #2) shall avoid interference to Link #1 over these resources. Accordingly, Link #1 can achieve a high reliability over the dedicated resources. On the other hand, the shared resources, as the name suggests, can be shared by more than one link (e.g., Link #1 and Link #2) simultaneously. Hence, the use of the shared resources by Link #2 may cause interference to Link #1 which is also using these resources. The shared resources provide for an increased link throughput, but have a lower reliability. Operations at Medium Access Control (MAC) layer can be performed based on the above resource allocation, which can be scheduled by the CCU 102 in accordance with e.g., interference levels measured in the cluster and data rates over the respective links.
In wireless communications, various feedback signals are required at different layers for various purposes. For example, at the MAC layer, an Acknowledgement (ACK) or Negative Acknowledgement (NACK) signal can be provided as a feedback signal for a data transmission, such that the sender of the data transmission can determine whether to resend the data transmission or not. In Long Term Evolution (LTE) for example, resources for ACK/NACK signals are allocated in a fixed, predefined manner. That is, for a data transmitted in a subframe having an index n, an ACK/NACK feedback signal is automatically scheduled to be transmitted in a subframe having an index n+k, where k is a fixed, predefined number for n. Such resource allocation is static and may not be suitable for the mmw-RAT network.
There is thus a need for an improved solution for resource allocation for feedback signals.